JPS60124149A - Four/six bit modulating method - Google Patents

Abstract

PURPOSE:To set up a DC component to ''0'', to increase the width of a detecting window and the minimum inversion interval and to reduce the maximum inversion interval by replacing 4-bit data in a binary data string divided in each 4 bits by a 6-bit code and NRZI-modulating the 6-bit code. CONSTITUTION:An input data string is divided in each 4 bits and converted into 6-bit codes in accordance with a conversion table shown in table (I) by a 4/6 bit conversion part 3 and the 6-bit codes are modulated and outputted by/from an NRZI conversion part 2. The 6-bit code is selected when the difference between the ''high'' period and ''low'' period of a signal of the code itself is ''0'', i.e. the total digital value is ''0''. The sum of codes setting the minimum inversion interval to 2T/3 and the maximum inversion interval to 2T is 18 codes. These code words are satisfied with the conditions of the minimum inversion interval and the maximum inversion interval even at the connection parts of the code words. A data word consisting of 4 bits requires 16<= more code words.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a 4-6 modulation method that can be used for transmitting, recording and reproducing digital signals.

Conventional Structures and Their Problems In recent years, various modulation methods have been used for the purpose of more stably recording and reproducing one recording/reproduction when recording and reproducing digital signals on optical or magnetic TiSF tapes. The 4-5 modulation method, which is a typical conventional modulation method, will be described below with reference to the drawings. Figure 1 shows a block diagram of the conventional 4-5 modulation method. This is a conversion table for converting 4-bit data into 5-bit 9-bit data in one line.

4-5'&J1. configured as above. ', 1 method will be explained below.' The 0-manual binary data string is divided into 4-bit units in the 4-5 converter (1) and converted into the conversion table shown in Table 1 according to the value of each 4-bit. Each of the bases is replaced with a 5-hit code, 1, and in the NILZI variable part (2), 4-
5. In the bit string after conversion, the output error signal is inverted at a location where there is a 1 bit, and at a 0 bit, the previous signal level is maintained as it is, so-called NRZI modulation is performed and then output. However, with the above conversion rule, the DC component, which is the difference between the sum of the No and No Table 1 periods of the modulated signal and the sum of the low periods, does not become 0; If a recording medium that does not pass through the transmission 1 is used, reproduction becomes extremely difficult.For example, in a recording/reproduction system using a rotating head coupled through a tortoise rotary transformer, the rotary transformer is an AC coupling element. Therefore, the recording current waveform having a DC component is distorted.

In order to solve the above problems, ZM (Zer.

A conventional modulation method is called "Modulation". This is a modulation method devised to convert a 1-bit L data word into a 2-bit code word so that the DC component becomes O.

However, in the above modulation method, 1 detection window width 1) i
Q, 5T', there is a problem that when performing high-density recording and reproduction, the margin of the detection window is small, making it difficult to perform one reproduction.

OBJECTS OF THE INVENTION An object of the present invention is to provide a modulation method that allows the direct current component to become completely O, increases the detection window width and minimum inversion interval as much as possible, minimizes the maximum inversion interval as much as possible, and makes the hardware simple. It is to provide.

Structure of the Invention In order to achieve the above object, the present invention converts a binary data string into four
The data is divided into bits, each 4-bit data is replaced with a corresponding 6-bit code according to the value of 7, and the code string is NRZI modulated. This completely removes the DC component. 0, the detection window width and the minimum reversal interval can be increased, and the maximum reversal interval can be decreased.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows a block diagram of a 4-6 modulation method in one embodiment of the present invention. In FIG. 2, (a) rJ: 4-a converter 1 (2) is NILZI
This is the conversion section. Table 2 is a conversion table for converting the manual 4-bit data into a 6-bit code in the 4-6 converter (3). The 4-6 conversion method of this embodiment configured as described above. will be explained below. First, the input categorization unit is the 4-6 converter (
3), it is divided into 4 bits, converted into a 6-bit code according to the conversion table in Table 2, and then converted into a 6-bit code in the NRZI conversion section (2).
NRZI modulation is performed and output.

The 6-bit code in Table 2 is selected as follows.The difference between the high period and low period of the 6-bit code itself is 01, that is, the digital sum value (hereinafter abbreviated as D8).
is 0, and the minimum inversion interval is "/Bs. The total number of codes in which the maximum inversion interval is 8T/8 is 18.

These codewords also satisfy the minimum inversion interval and maximum inversion interval conditions at the codeword connection. Since the number of bits of a data word is 4 bits, the number of code words satisfying one condition may be 16 bits or more. Therefore 11Nl+! ++
Select 16 code words from among the code words. Since a self-clock is generated from a signal during endogeneity, the smaller the signal inversion interval, the more advantageous it is. Therefore, those in which the maximum inversion interval of 8'/8 does not occur are selected preferentially. Maximum reversal interval is 2T
Since there are 15i code words, all of them are used in Table 2. The remaining one is “001001”, “00”
1011'', ``001110'' must be selected from among the 08 codes. In this embodiment, ``001011'' is used from the viewpoint of selecting a code word with a large number of 1 inversions. In Table 2, the data word ``0110'' ” corresponds to this.

Effects of the Invention As is clear from the above explanation, the present invention divides the human-powered binary data data 1j into 4 bits, converts each bit data into a corresponding 6-bit code according to its value, and converts it into flH4Z.
Since I modulation is performed, the DC component can be reduced from 0 to 1, and the detection window width, minimum inversion interval can be increased, and maximum inversion interval can be decreased, making it possible to increase the density of recording and transmission. Effects can be obtained. Particularly when the transmission system uses a transmission system using a transmission system, the effect that the DC component is 0 has the effect of increasing the noise margin of the reproduced waveform.

In addition, since the present invention associates one code word with one data word, it is difficult to use the hard When the clothes become easier (1) there are better effects.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional 4-5 modulation method, and FIG. 2 is a block diagram of a 4-6 modulation method in an embodiment of the present invention. -6Km
Department agent Yoshihiro Morimoto Figure 1

Claims (1)

[Claims] 1. Divide the binary data string into 4-bit units Replace each 4-bit data with the corresponding 6-bit code according to its value and modulate the code string with NRZI 4-6 father v
The 4-6 modulation method 03.6-bit code according to claim 1 is characterized in that the ra method 02.6-bit code is assigned its own DC component of 0. /8) The 4-6 modulation method e according to claim 1 or 2, characterized in that the maximum inversion interval is selected to be 4.